(1) Field of Invention
This invention relates to hydrocyclone separators for liquid suspensions, and more particularly to a hydrocyclone separator which is capable of treating highly concentrated slurries with versatile components.
(2) Description of Prior Art
In the treatment of urban refuse, as a pretreatment for the waste paper refining or prior to methane fermentation of organic waste materials such as kitchen garbage, the urban refuse is added to water to make a slurry which contains large amounts of paper, kitchen garbage and other fibrous materials, and then heavy extraneous components such as glass, stones, metals and the like are separated from the slurry. However, it has been revealed by a number of experiments that conventional hydrocyclone separators are incapable of handling such a slurry and easily become inoperative due to choking of underflow nozzles. The slurry, which is undergoing the separating effects of the hydrocyclone, rapidly loses its flowability by thickening in the vicinity of the underflow discharge nozzle and stagnates there. If the discharge rate through the underflow nozzle is increased to avoid this, fragments of paper and kitchen garbage will flow out along with the underflow discharge, lowering the percentage of recovery which is the very purpose of the operation. On the other hand, if the slurry is fed to the hydrocyclone in a lower concentration to make the separation easier, it becomes necessary to conduct the treatment of a large amount of resulting waste water for environmental protection, which is economically a great disadvantage to the waste disposal system as a whole.
Thus, it has been difficult or almost impossible for the conventional hydrocyclone separators to conduct precise separation by imparting a high pressure to a slurry feed of high concentration or density.
It is therefore an object of the present invention to provide a hydrocyclone separator which has a screw conveyor type forced discharge means at the underflow discharge end and which can separate slurries of the type which falls in the operable range of ordinary hydrocyclones, as well as slurries of high concentration which contain heavy extraneous materials along with fibrous materials such as paper, kitchen garbage and the like, in a stable operating condition and with a high degree of separation.
It is another object of the present invention to provide a hydrocyclone separator with a screw conveyor type forced discharge means, which can effect the separation of slurries having a higher degree of concentration than slurries within the operating ranges common with ordinary conventional hydrocyclones.
It is a further object of the present invention to provide a hydrocyclone separator with a screw conveyor type forced discharge means which is driven by a variable speed motor to control the underflow discharge rate according to the conditions of the slurry to be treated.
It is a still further object of the present invention to provide a hydrocyclone separator with a screw conveyor type forced discharge means, which is further provided with an air supply passage extending axially through the rotational axis of the screw conveyor to feed air into the hydrocyclone for maintaining an air column therein to sustain an effective separation performance.
It is still another object of the present invention to provide a hydrocyclone separator which, in contrast to the conventional counterparts, in which only the size and the proportion of the hydrocyclone and the pressure of feed are the controllable factors and in which the pressure of feed is the sole variable factor in operation, additionally allows control of the discharge rate through the underflow nozzle and of the flow rate of air fed from the air feeder, thereby permitting control of the operating conditions with a higher degree of freedom to suit the particular property of the slurry to be treated.